#surfacetension — Public Fediverse posts

Plucking Droplets

A sudden breeze can pluck droplets hanging from a stem. Here, researchers recreate that phenomenon in the laboratory. With a close-up view and high-speed images, we can enjoy every detail of the detachment and break-up. As the wire pulls away, it drags a liquid sheet off the droplet. The thicker rims on either side of the sheet eventually collide, creating a jet that stretches, deforms, and, at last, breaks. (Video and image credit: D. Maity et al.)

Making a Star-Shaped Droplet

We usually think of surface tension turning droplets into spheres in order to minimize their area. But spheres aren’t the only shape surface tension can enforce. Here, researchers suspend tiny droplets of oil in a soapy fluid. At the right temperature, these droplets form a crystalline surface while the fluid within remains liquid. As in the fully liquid droplet, surface tension tries to minimize the shell’s surface energy, enabling it to take on many different shapes.

In this study, researchers demonstrate that the shell-enclosed droplets can even change, reversibly, from a hexagon to a six-pointed star and back. The transformation is shown above, in an experiment that gradually changes the droplet’s temperature–and, thus, its surface tension.

Although shape changes similar to these have been described before, this experiment was the first where the shell’s defects–the vertices of the hexagon–don’t shift during the transformation. (Video, image, and research credit: C. Quilliet et al.; via APS)

A Bubbly Heart

Next time you fill your water bottle, watch closely and see if you can spot a bubble heart like these. When a jet falls into a pool, it pulls air in with it. The low pressure of the jet pulls bubbles inward, even as shear pulls the bubbles downward with the sinking liquid. If the bubbles are large and there’s enough momentum in the jet, the lower portion of the bubble will get pulled into a conical shape, while the upper portion remains a hemisphere. That forms one lobe of the heart. The other half requires a second bubble. But with a little patience and luck, you can form a complete heart. Happy Valentine’s Day! (Image credit: S. Tuley et al.)

Caught in a Spider’s Web

Grains of pollen are caught amid droplets on a spider’s web in this award-winning image by John-Oliver Dum. How droplets behave on fibers has been a popular topic in recent years with research on how droplets nestle into corners, how they slide on straight or twisted wires, the patterns formed by streams of falling drops, and what happens to a droplet on a plucked string. (Image credit: J. Dum; via Ars Technica)

A Soft Cell in Microgravity

There are many shapes that can be tiled to fill space, but nearly all of them have sharp corners. Last year, mathematicians identified a new class of shapes, known as “soft cells,” that feature curved edges and faces but very few sharp corners. Like traditional polyhedrals, soft cells can tile to fill a space completely without overlapping or gapping.

Now the researchers, with some help from astronauts aboard the ISS, have brought one of their soft cells to life. Using an edge skeleton to guide the shape, astronaut Tibor Kapu filled the skeleton with water, which, in microgravity, formed a perfect soft cell, complete with faces curved by surface tension to their minimal area. See it in action below. (Image and video credit: HUNOR/NASA; research credit: G. Domokos et al.; via Oxford Mathematics)

https://www.youtube.com/shorts/EyMbqPUKl80

Marangoni Bursting With Surfactants

A few years ago, researchers described how an alcohol-water droplet atop an oil bath could pull itself apart through surface tension forces. Dubbed Marangoni bursting, this phenomena has shown up several times since. Here, researchers explore a twist on the behavior by adding surfactants to see how they affect the bursting phenomenon. (Video and image credit: K. Wu and H. Stone; via GFM)

#flowVisualization #fluidDynamics #instability #MarangoniBursting #physics #science #surfaceTension #surfactant

The Balvenie

Photographer Ernie Button explores the stains left behind when various liquors evaporate. This one comes from a single malt scotch whisky by The Balvenie. The stain itself is made up of particles left behind when the alcohol and water in the whisky evaporate. The pattern itself depends on a careful interplay between surface tension, evaporation, pinning forces, and internal convection as the whisky puddle dries out. (Image credit: E. Button/CUPOTY; via Colossal)

#alcohol #deposition #evaporation #fluidDynamics #fluidsAsArt #physics #science #surfaceTension

Deep Breaths Renew Lung Surfactants + A Special Announcement

Taking a deep breath may actually help you breathe easier, according to a new study. When we inhale, air fills our alveoli–tiny balloon-like compartments within our lungs. To make alveoli easier to open, they’re coated in a surfactant chemical produced by our lungs. Just as soap’s surfactant molecules squeezing between water molecules lowers the interface’s surface tension, our lung surfactants gather at the interface and lower the surface tension, making alveoli easier to inflate.

But things are a little more complicated in our lungs than in our kitchen sink because of our constant cycle of breathing, which stretches and compresses our lungs’ surfaces and surfactant layers. Imagine a flat interface, lined with surfactant molecules; then stretch it. As the interface stretches, gaps open between the surfactant molecules and allowing molecules from the interior of the liquid to push their way to the newly stretched interface, changing the surface tension. If the interface gets compressed, some of the excess molecules will get pushed back into the liquid bulk.

In looking at how lung surfactants respond to these cycles of compression and stretching, the researchers found that the lung liquid develops a microstructure during cycles of shallow breathing that makes the surface tension higher, thus making lungs harder to fill. In contrast, a deep breath like a sigh replenished the saturated lipids at the interface, lowering surface tension and making lungs more compliant. So a deep sigh actually can help you breathe easier. (Image credit: F. Møller; research credit: M.. Novaes-Silva et al.; via Gizmodo)

P.S. — I’ve got a book (chapter)! Several years ago, I joined an amazing group of women to write two books (one for middle grades and one for older audiences) about our journeys as scientists. And they are out now! In fact, today we’re holding a “Book Bomb” where we aim for as many of us as possible to buy the book(s) on the same day. If you’d like to join (and get ahead on your gift shopping), here are (affiliate) links:

• Persevere, Survive, and Thrive (including my story of becoming a science communicator): Amazon, Bookshop.org
• For All the Curious Girls: Amazon, Bookshop.org

#biology #fluidDynamics #lungs #physics #science #surfaceTension #surfactants

Wave Energy Through the Meniscus

Even small changes to a meniscus can change how much wave energy passes through it. A new study systemically tests how meniscus size and shape affects the transmission of incoming waves.

As seen above, the meniscus was formed on a suspended barrier. By changing the barrier size and wettability as well as the characteristics of incoming waves, researchers were able to map out how the meniscus affected waves that made it past the barrier.

In particular, they found that drawing the meniscus upward by raising the barrier would, at first, enhance wave transmission but then suppressed wave energy as the barrier moved higher. They attributed the change in behavior to an interplay between water column height and meniscus inclination. (Research and image credit: Z. Wang et al.; via Physics World)

#capillaryWaves #fluidDynamics #meniscus #physics #science #surfaceTension #waves

Espresso in Slow-Mo

Espresso has some pretty cool physics. But it’s also just lovely to watch in slow motion. This video offers a look at the making of an espresso shot at 120 frames per second (though you can also enjoy a 1000 fps version here). Watching the film form, expand, and break up at the beginning and end of the video is my favorite, but watching how the occasional solid coffee grains make their way into and down the central jet is really interesting also. (Video and image credit: YouTube/skunkay; via Open Culture)

#espresso #flowVisualization #fluidDynamics #fluidsAsArt #highSpeedVideo #physics #science #surfaceTension

How Insects Fly in the Rain

Getting caught in the rain is annoying for us but has the potential to be deadly for smaller creatures like insects. So how do they survive a deluge? First, they don’t resist a raindrop, and second, they have the kinds of surfaces water likes to roll or bounce off. The key to this second ability is micro- and nanoscale roughness. Surfaces like butterfly wings, water strider feet, and leaf surfaces contain lots of tiny gaps where air gets caught. Water’s cohesion — its attraction to itself — is large enough that water drops won’t squeeze into these tiny spaces. Instead, like the ball it resembles, a water drop slides or bounces away. (Video and image credit: Be Smart)

#biology #butterfly #cohesion #droplets #fluidDynamics #hydrophobic #insects #physics #science #superhydrophobic #surfaceRoughness #surfaceTension

The Mystery of the Binary Droplet

What goes on inside an evaporating droplet made up of more than one fluid? This is a perennially fascinating question with lots of permutations. In this one, researchers observed water-poor spots forming around the edges of an evaporating drop, almost as if the two chemicals within the drop are physically separating from one another (scientifically speaking, “undergoing phase separation“). To find out if this was really the case, they put particles into the drop and observed their behavior as the drop evaporated. What they found is that this is a flow behavior, not a phase one. The high concentration of hexanediol near the edge of the drop changes the value of surface tension between the center and edge of the drop. And that change is non-monotonic, meaning that there’s a minimum in the surface tension partway along the drop’s radius. That surface tension minimum is what creates the separated regions of flow. (Video and image credit: P. Dekker et al.; research pre-print: C. Diddens et al.)

#2024gofm #droplets #evaporation #flowVisualization #fluidDynamics #instability #physics #science #surfaceTension

Active Cheerios Self-Propel

The interface where air and water meet is a special world of surface-tension-mediated interactions. Cereal lovers are well-aware of the Cheerios effect, where lightweight O’s tend to attract one another, courtesy of their matching menisci. And those who have played with soap boats know that a gradient in surface tension causes flow. Today’s pre-print study combines these two effects to create self-propelling particle assemblies.

The team 3D-printed particles that are a couple centimeters across and resemble a cone stuck atop a hockey puck. The lower disk area is hollow, trapping air to make the particle buoyant. The cone serves as a fuel tank, which the researchers filled with ethanol (and, in some cases, some fluorescent dye to visualize the flow). Like soap, ethanol’s lower surface tension disrupts the water’s interface and triggers a flow that pulls the particle toward areas with higher surface tension. But, unlike soap, ethanol evaporates, effectively restoring the interface’s higher surface tension over time.

With multiple self-propelling particles on the interface, the researchers observed a rich series of interactions. Without their fuel, the Cheerios effect attracted particles to each other. But with ethanol slowly leaking out their sides, the particles repelled each other. As the ethanol ran out and evaporated, the particles would again attract. By tweaking the number and position of fuel outlets on a particle, the researchers found they could tune the particles’ attractions and motility. In addition to helping robots move and organize, their findings also make for a fun educational project. There’s a lot of room for students to play with different 3D-printed designs and fuel concentrations to make their own self-propelled particles. (Research and image credit: J. Wilt et al.; via Ars Technica)

#3DPrinting #CheeriosEffect #DIYFluids #evaporation #flowVisualization #fluidDynamics #marangoniEffect #physics #science #surfaceTension

Predicting Droplet Sizes

Squeeze a bottle of cleaning spray, and the nozzle transforms a liquid jet into a spray of droplets. These droplets come in many sizes, and predicting them is difficult because the droplets’ size distribution depends on the details of how their parent liquid broke up. Shown above is a simplified experimental version of this, beginning with a jet of air striking a spherical water droplet on the far left. In less than 3 milliseconds, the droplet has flattened into a pancake shape. In another 4 milliseconds, the pancake has ballooned into a shape called a bag, made up of a thin, curved water sheet surrounded by a thicker rim. A mere 10 milliseconds after the jet and drop first meet, the liquid is now a spray of smaller droplets.

Researchers have found that the sizes of these final droplets depend on the balance between the airflow and the drop’s surface tension; these two factors determine how the drop breaks up, whether that’s rim first, bag first, or due to a collision between the bag and rim. (Image credit: I. Jackiw et al.; via APS Physics)

#atomization #bag #droplets #flowVisualization #fluidDynamics #physics #science #sprays #surfaceTension

If you sandwich a viscous fluid between two plates and inject a less viscous fluid, you’ll get viscous fingers that spread and split as they grow. This research poster depicts that situation with a slight twist: the viscous fluid (transparent in the image) is shear-thinning. That means its viscosity drops when it’s deformed. In this situation, the fingers formed by the injected (blue) fluid start out the way we’d expect: splitting as they grow (inner portion of the composite image). But then, the tip-splitting stops and the fingers instead elongate into spikes (middle ring). Eventually, as the outer fluid’s viscosity drops further, the fingers round out and spread without splitting (outer arc of the image). (Image credit: E. Dakov et al.; via GoSM)

https://fyfluiddynamics.com/2024/04/evolving-fingers/

#2024gosmp #flowVisualization #fluidDynamics #HeleShawCell #instability #nonNewtonianFluids #physics #SaffmanTaylorInstability #science #shearThinning #surfaceTension #viscosity #viscousFingering

Good news for clumsy divers: Physics holds the key to less-painful belly flops - Brown researchers set up a belly flop-like water experiment using a ... - https://arstechnica.com/?p=1981301 #air/waterinterface #harmonicoscillator #marineengineering #fluidmechanics #surfacetension #hydrodynamics #bellyflops #science #physics #diving

I just thought the standing waves set up in this stream of water coming out of my water pitcher filter were mesmerizing. Video is 4x speed so you can see the evolution of the wave pattern as the pitcher fills.

#fluids #fluiddynamics #laminarflow #surfacetension #standingwave

It's been some time since my last #toot ⏰.
A lot is going on the last few weeks. I've been learning much about volume of fluid #VOF and #surfacetension and having finally some success with boundary conditions 😁. Hope to share some more in the upcoming weeks.

Besides that, I've just browsed the first few pages of #PRL recent and while I think they do a good job of representing different areas of #physics, there is a lot of high energy physics 🔄 💥

#SteveMould - Can #Water #Solve A #Maze?

https://www.youtube.com/watch?v=81ebWToAnvA&ab_channel=SteveMould

#Math #Maths #Science #Physics #Fluid #Fluids #FluidDynamics #Flow #FluidFlow #Path #SolvePath #SurfaceTension

'Dream' || Grand Bend, Ontario, Canada || March 2023

#Nature #NaturePhoto #NaturePhotography #NatureLovers #Ontario #ExploreOntario #DiscoverON #Canada #ExploreCanada #PhotooftheDay #Instaphoto #DailyPhoto #PhotoduJour #CanonPhotographer #Photographer #Photography #фотография #Fotografie #Photographie #PhotoPrints #GrandBend #ShareCanGeo #LakeHuron #GreatLakes #Rock #Macro #SurfaceTension #Water #Rocks

Sorry for decreasing the signal/noise ratio, but I just realized the obligatory tag cloud is obligatory.
#science #mechanics #fluidmechanics #simulation #numerical #numericalmethods #data #datavisualization #multiphase #twophase #flow #maths #mathematics #physics #engineering #CORIA #Sorbonne #turbulence #fragmentation #emulsions #levelset #VOF #volumeoffluid #largeeddysimulation #fsi #fluidstructure #droplets #bubbles #surface #surfacetension #geometry #topology